Similar to the friend zone, but much, much worse. Simply put, it is when the girl you have feelings for cares about you to the extent that she thinks of you as not just a friend but as her "brother", making any potential chance for a relationship disappear.

Guy 1: God, I'm in the friend zone...

Guy 2: Shut the hell up, at least the friend zone has a way out. I'm in the brother zone. I'm totally fucked.

When you're interested in taking your friendly relations with a girl to the next level and she rejects you, with her reason being you are like an older or younger brother figure for her. Basically a dead end to any further advances.

Guy: "So I was wondering if you'd like to go out on a real date with me sometime..."

Girl: "Ha ha no, that would be too weird! You're like a brother to me!"

The ultimate level of friendzone invented by women. It is like an inescapable pit of hell where the female you have romantic interest in, will destroy your all hope of having an romantic relationship with her and will turn you into an ultra super mega ultimate friend slash brother. The term is very popular in some countries where male-female "friendship" isn't a norm yet. Especially south asian ones like India, Pakistan or Bangladesh where it is known as Bhai Zone . Unlike Friend zone there is no hope of escaping brother zone. And it involves much more suffering. The only thing a guy can do after being friendzoned is ignore the girl although that is almost impossible as the girl will want help and favors from the guy as a brother.

The zone even further out then the 'friend zone'. You are the ultimate friend, 'pretty much like my brother!'. This can apply to women as well, that of being in the 'sister zone'. Once you're in one of these zones though, it's best to come to the realization that you only make out of one zone. Brother zone - moves up to friend zone - friend zone sometimes can move past and become that of a dating partner (when lucky).

Matt: Why are you always hanging with Alicia, why don't you ask her out already?
Dan: Can't man. I'm in the brother zone.
Matt: Crikey!!